1. Field of the Invention
The present invention relates to the structure of the backlight of an LCD (liquid crystal display), in particular, the structure by which the frame portion of the display section can be narrowed and the device's weight can be reduced.
This application is based on Patent Application No. Hei 10-220782, filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
The LCD, used as a display device, is mounted in a variety of electronic devices. A laptop (or notebook) personal computer is a typical electronic device employing a large-size liquid display screen. In recent laptop personal computers, the main screen size has been standardized to "A4 size" or "B5 size", and there is competition to develop thinner and lighter screens at these standard sizes. Development is being carried out to increase the area of the LCD itself within the limited main screen size. In order to increase the area of the LCD, it is important to determine how the outer edge of the LCD screen, that is, the frame portion of the main screen, can be narrowed.
FIG. 4 is a general perspective view showing the backlight portion of a conventional transmission-type LCD, and FIG. 5 is a sectional view thereof.
As shown in FIGS. 4 and 5, the backlight of such a conventional transmission-type LCD generally comprises light-introducing plate 23 for introducing light, input from an end face the plate, in a manner such that the LCD panel is irradiated by the light, cold cathode tube 26 for radiating light towards the inside of the light-introducing plate 23; reflector 27 for effectively reflecting the light radiated from the cold cathode tube 26 so as to direct the reflected light towards the end face of the light-introducing plate 23; diffusion plate 30, disposed on the upper face of the light-introducing plate 23, for diffusing the light (introduced from the light-introducing plate 23) towards the outside; and reflection plate 25, attached to the bottom face of the light-introducing plate 23, for reflecting the light transmitted through the light-introducing plate 23 so as to direct the reflected light towards the front face. Reference numeral 21 indicates an LCD panel, and reference numeral 22 indicates a display section.
In the above structure, lower-voltage electrode 26b and higher-voltage electrode 26a are provided at both ends of the cold cathode tube 26, and the lower-voltage electrode 26b is connected with connection (wiring) line 31. In order to easily connect the cold cathode tube 26 with an electric source, the connection line 31 is extended to the connection point of the higher-voltage electrode 26a and such an arrangement prevents the narrowing of the screen frame.
In order to make the LCD thin and to make the screen frame narrow in the above structure of the backlight, Japanese Unexamined Patent Application, First Publication, No. Hei 9-230341 discloses an arrangement (shown in FIG. 6) in which a sheet-type connection line 31 is adopted and is disposed on the upper face of the light-introducing plate 23, thereby reducing the size and weight of the device.
However, in the above structure, if the cold cathode tube 26 and reflector 27 are disposed in the display area corresponding to the display section 22 of LCD panel 21, the upper portion of the reflector 27 is not irradiated, so that the cold cathode tube 26 and reflector 27 must be disposed outside the above display area. Therefore, it is difficult to further narrow the frame of the LCD.